Heat shield materials and systems are utilized for protecting various spacecraft types, such as crew exploration vehicles (hereinafter “CEV”) and aeroentry craft, from the very high temperatures generated upon re-entry into the earth's atmosphere. The design of such materials and systems for current and future space-related missions requires heat shield materials which can safely and reliably shield the spacecraft from the potentially damaging effects of heat flux levels as high as about 1,000 W/cm2 and surface pressures up to about 0.7 atmospheres.
One approach for providing heat shield materials for use in spacecraft re-entry applications involves use of a high mass density TPS material (e.g., Avcoat 5026-39/HC-G) which is injected into individual cells of a honeycomb matrix structure. However, use of high density TPS materials is undesirable in spacecraft related applications where mass is a critical factor.
Another approach for providing heat shield materials for use in spacecraft re-entry applications involves packing a cork and silicone-based super light, ablative (hereinafter “SLA”) material (e.g., SLA-561 V) into a honeycomb matrix structure, e.g., a flexible or rigid phenolic honeycomb. The SLA-561 V material allows for monolithic application to the heat shield utilizing techniques developed for SLA applications on the Viking Heat Shield. The manufacturing process of SLA-561 V involves thoroughly mixing ground cork, silicone, silica fibers, silica and phenolic microballons and packing the mixture into the cells of the phenolic honeycomb core. However, a drawback associated with this approach is difficulty in mounting/fastening the thus-formed honeycomb structure to structural substrates, such as those encountered on CEVs.
In view of the foregoing, it is apparent that a clear need exists for improved ablative TPS materials and systems which advantageously provide improved thermal performance and physical properties, lower mass density, ease of application to structural substrates, and scalability for fabrication of large, seamless heat shields necessary for current and future spacecraft-related re-entry applications.